Protractor



B. K. FISHER.

PROTRACTOR.

APPLICATION FILED MAR.24, 1917.

1,350,27 3. Patented Au 17, 1920.

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Gl tozneq K. FISHER.

PR'OTBACTOR.

APPLICATION FILED MAR. 24, 1917.

1,350,273. Patented Aug! 17, 1920.

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PRO'TRACTOR. v v APIPLICATION FILED MAR. 24, 1917. 1,350,273. Patented A g- 17, 1920.

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Qnocnko'o UNITED STATES BENJAMINK. FISHER, or-s'r. LOUIS, MISSOURI.

PROTRACTOR.

Specification of Letters Patent.

Patented Aug. 17, 1920.

Application filed March 24, 1917. Serial No. 157,084.-

'1 '0 all 407mm, it may concern:

Be it known that I, BENJAMIN K. FISHER, a citizen of the United States, and resident of St. Louis, in the State of lVIissouri, have invented certain new and useful Improvements in Prom-actors of which the following is a specification.

My invention relates to protractors and it is my purpose to provide a'protractor embodying an improved construction whereby various operations incident to drafting and plotting can be performed with ease and facility and without resorting to any complicated mathematical computation.

Specifically speaking it is my purpose to provide a protractor which will greatly facilitate the operation of dividing a circle or of drawing a series of tangents.

I will describe my invention in the best forms known to me at'present but it will be understood that they are susceptible to changes in forms and proportions and to desirable additions with the exercise of only ordinary mechanical skill and without departing from the spirit of my invention.

In the drawings chosen to illustrate my invention the scope whereof ispointed out in the claims.

Figure 1 is a plan view of a protractor constructed in accordance with my invention and showing the manner of utilizing the same to divide a circleinto equal parts;

Fig. 2, an edge view of the protractor partlyvin section;

3, a view similar toFig. 1 showing a modified form of my invention;

Fig. 1, a section onthe line 4-4 of Fig. 3;

Fig. 5, a view similar to Fig. 1 showing another modified .form of my invention particularly adapted for drawingtangents, and

Fig. 6, a section on the line 6-6 of Fig. 5. Referring now to Figs. 1 and 2 my improved protractor is shown as comprising a body 10 formed of a suitable transparent material such as celluloid. The body 10 is substantially semi circular in shape and provided with an extension 11 and a straight ruling edge 12 common to both the semicircular portion of the body and the extension 11. Provided on the body 10 is a plurality of rows ofdivision points 13 arranged incidence with the line 24 by concentric to a pivot pin 14' mounted in the body 10 in line with the ruling-edge 12. The rows of division points 13 can be designed respectively for any given division. In this instance the points of the various rows are arranged to divide a circle into twentieths, twenty-fourths, twentyeighths, thirty-seconds, thirty-sixths, fortieths, fortyfourths and forty-e1ghths, but this arrangement can be varied to suitthe capacity desired. the actual shape of the body of the protractor is immaterial, the only essential being that a ruling edge be provided and that the rows of division points be arranged concentric to the pivot of the body 10.

In order to divide the circle 15 indicated in Fig. 1 into thirty-sixths it is only necessary to engage the pivot pin 14 in the sur face to be marked at the center of the circle 15 and the line 16 drawn. A dot 17 should then be placed on the surface to be marked at the end of the thirty-sixth row remote from the line'16. The protractor is then rotated until the first division point of the thirty-sixth row coincides with thedot 17 when the line 18 is drawn. The protractor is again rotated until the second division point of the thirty-sixthrow coincides with the dot 17 when the line 19 is drawn. This operation is repeated until the required Furthermore, itmay be stated that number of divisions of the circle 15 is had.

It will be observed that by making the body 10 of'transparent material thecoincidence of the division" points of the various rows with any selected dot on the surface to be marked can be readily ascertained,

In the modified form of my invention illustrated in Figs. 3 and the body 10 is formed of opaque material and in order to carry out the principle of the invention 'I provide a transparent arm 20 carrying at its respective ends pins 21 and 22. The former is detachably engageable in a recess 23 in the body 10 and constitutes the pivot of said body. The pin 22 is adapted to be engaged in the surface to be marked so as to hold the arm 20 in a fixed relation to said surface, This arm 20 is provided with a hair line 24 and in the operation of the device the division points of the rows 13 are brought into comovement of enabled to provide the reverse side of the body 10 with various scales common to protractors and by removing the arm 20 can utilize the body of the protractor in such manner as will employ the scales on the reverse side.

. In the use of this form of the invention it is only necessary to set the arm 20 so as to bring the line 24- into coincidence with a division point of a desired row 13 and then draw the line 16. The body 10 is then r0- tated to bring the next division point of said rev; into coincidence with the line 24 when the line 18 is drawn. This operation is repeated until the desired number of divisions are. had.

In the modified form of my invention illustrated in Figs. 5 and'6 I utilize the principle involved for the purpose of drawing a number of tangents having corresponding relation to a given circle. In this form of the invention I construct the bodylO of transparent material and provide along the ruling edge 12 a number of prongs '25 for the purpose of interlocking a piece of card board or like material 26 with the body 10. In this form of my invention the circle to whichthe lines are to be drawn tangent is indicated at 27' and the body 10 1s applied with its pivot coincident with the center of. the. circle 27. The card board or the. like 26 is then pressed on the prongs 25 in such, position as to bring the edge 28 thereof tangent to the circle 27 and the first tangent drawn. The desired dot 17 is then placed on thesurface to be marked and the body 10 is rotatedto bring the division points of agiven row 13 into successive coincidence with the dot and for each coincidence specified a tangent 29 is drawn with the edge 28 of the'card board utilized as a ruling edge. 7 V

I. desire to'state wherever I use the word body in the claims I intend to include within its scope a body formedojf either a single piece of material as shown in Fig. 1 or of a plurality of pieces of material as shown in'Fig. 5; While I have described my invention as adapted for certain specific uses it will be obvious that it is in no way limited to such uses but can be employed for any and all operations to which it may be applicable. r 2

What is claimed is 1. A protractorcomprising a body having I a ruling edge and a fixed axis ofrotation about which it is adapted to be rotated over a surface to be marked, and through which body an indicated point fixed relatively to the surface to be marked can be observed, said body having a plurality of rows'of division points indicated thereon and arranged concentric with the axis of rotation of the body, whereby the rotation of the body will bring the division points of a given row successively into coincidence with an indicated point fixed relatively to the surface to be marked to determine successive positions of the ruling edge.

2. A protractor comprising a body'having a ruling edge and a fixed axis of rotation about which it is adapted to be rotated over a surface tobe marked, said body having a plurality of rows of division points indicated thereon and arranged concentric with the axis of rotation of the body for movement into successive observablecoincidence with an indicated point fixed relatively to the surface to be marked to determine indicated thereon and arranged concentricwith the axis of rotation of the body where-- by the rotation of the body will bring the division points of a given row successively into coincidence with an indicated point fixed relatively to the surface to be marked to determine successive positions of the ruling edge. 7 v In testimony whereof I hereunto. afli x my signature in the presence of two witnesses.

V BENJAMIN K. FISHER. Witnesses: p i

ALBERT VVnNzLIoK, RoMAN S'rnANz; 

